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					NETWORK SECURITY




                   Source: Wired
         Computer and Network Attack Taxonomy
    Attackers        Tools                             Access                         Results       Objectives

      Hackers        User        Implementation   Unauthorized   Process    Files      Corruption    Challenge,
                   Command        Vulnerability     Access                                 of          Status
                                                                                      Information
       Spies        Script or       Design        Unauthorized             Data in     Disclosure   Political Gain
                    Program       Vulnerability       Use                  Progress        of
                                                                                      Information
     Terrorists    Autonomous    Configuration                                         Theft of     Financial Gain
                      Agent      Vulnerability                                         Service

     Corporate       Toolkit                                                          Denial-of-       Damage
      Raiders                                                                          Service

    Professional   Distributed
     Criminals        Tool

      Vandals       Data Tap




                                                      Time
Source: Dissertation of John D. Howard, CMU, 1997
               Group Task
• Get together on groups of 3-5 people
• Discuss an attack that one of your group
  members have experienced or heard about
• For that attack, mark within which cells the
  attack belongs
• Five minutes
Securing Resources
         Threats to Security
• Physical security
• Access Security
   – Unauthorized access into a computer
   – Tapping into a data communications line
• Personnel
   – Misuse by authorized personnel
• Natural Disaster
• Computer Viruses, Worms, Logic Bombs.
• Denial of Service Attacks
      Security concepts/terminology

Need to address following issues:
• Secrecy/Privacy: guarantee that information
  given will not be misused
• Authenticity: data provided to user must be
  authentic (i.e., is it really coming from X?)
• Integrity: data stored in system must not be
  corrupted.
• Non-repudiation: A mechanism which prevents a
  user from denying a legitimate, billable charge.
Phishing
Which one would YOU trust?
User Identification and Authorization
 • Passwords
    – kept in encrypted file
    – should be changed frequently
    – automatic expiration
 • Ultra-sensitive applications
    – layered IDs (passwords at several levels)
    – user profiles (restrictions on who can do what)
    – access levels (read, write, execute, purge)
    – combining menus and user profiles (let user see
      only those options available to her)
 Time and Location Restrictions
• Establish time intervals during which
  transaction is allowed
• Certain transactions can run only from
  certain locations
   – attach applications to terminals
   – maintain terminal profile

• Additional precautions on switched
  ports with dial-in access
   – call-back unit
   – restricted hours
   – safeguard telephone numbers
   – manual authentication in high
     security installations
               Other Methods
• Recognizing unauthorized access attempts
   – after 3 failed attempts disallow log-in for 5 minutes
   – permit fake log-in after several failed attempts
• Automatic log-off
   – log off anybody with no activity for 10 minutes
   – authentication for every transaction
• Transaction logs
   – every log-in is logged (date, time user id,
     unsuccessful attempts, terminal id, location)
No method is foolproof. These are delaying tactics.
Setting: Europe
Time: 1940-45



How?




 Securing Communications
              Data Encryption
• Symmetric Key Cryptography
  – Data encryption standard (DES), Bureau of standards
    (based on symmetric key)
     • 56-bit encryption key (now available in longer keys)
     • uses 16 iterations of rearrangement and substitution
       combinations
     • Its 72-quadrillion combinations were broken in 1997 by a
       group using distributed computing (14,000 computers) – lead
       by Colorado programmer Rocke Verser
• Public Key cryptography
  – (the other approach, covered later)
31798603996994715581310583186337934867429744958612
How much is?   1 Billion




                            30 bits
                            (9 zeros)



                    Source: http://www.kokogiak.com/
                    megapenny/default.asp
How much is?   10 Billion




                        40 bits
                        (12 zeros)
How much is?   1 Quadrillion




                        50 bits
                        (15 zeros)
How much is?   1 Quintillion




                        60 bits
                        (18 zeros)
How much is?   1 Octillion




                        128 bits
                        (38 zeros)



                             Previous collection
                             (enlarged for your
                             benefit)
     How much is?

             Number of pennies
             that can fit inside the
             Universe                                      300 bits
                                                           (90 zeros)




Thanks to Alexander Voronovich for help with calculation
                “RSA Laboratories currently recommends
                key sizes of 1024 bits for corporate use and
               2048 bits for extremely valuable keys like the
               root key pair used by a certifying authority “


                                                                                    2048 bits
                                                                                    (616 zeros)




Source:   http://www.rsasecurity.com/rsalabs/node.asp?id=2218 Downloaded 04/06/06
Symmetric Key Encryption




Encrypted message: DSPEZHKE
      Data encryption based on symmetric key
                      (A very old method)

• Divide plain text into groups of 8 characters. Pad with blanks
  at end (if necessary)
• Select an 8-character key
• Rearrange plain text by interchanging adjacent characters
  (first with second, third with fourth)
• Translate each character into a number (A-1, B-2, C-3, ....., Z-
  26, blank-0)
• Add the numbers of the key (Step 2) to the results of above
  step.
Data encryption based on symmetric key(contd.)

• Divide each sum by 27 and keep remainder
• Translate remainder back into character to yield the cipher
  text.
At the receiving end
• Perform the reverse operation (i.e., the same set of steps in
  reverse order) to restore the original text.
             Example
• DATA _COM
• ADATC_MO     rearrange characters
• 01 04 01 20 03 00 13 15 translate
  16 18 15 20 15 03 15 12 key vals.
   17 22 16 40 18 03 28 27 sum
   17 22 16 13 18 03 01 00 mod 27
• Q V P M R C A                 _ result
    PAP: Direct Password
    (Password authentication protocol)
                                                           GOT IT!
                                                        (That was easy)


                         “It’s me, and
                           here’s my
                        PASSWORD.”


                                   Access    Carrier       Remote LAN
                                 Equipment   Services      Access Server

                                                                    LAN
      • Simple password access
      • Vulnerable to snooping
(Source: Ascend Corp)
   CHAP: Secured Password Exchange                                                                  ?
   (Challenge authentication protocol)

                                             1. “It’s me, Luigi”
                        3. “Here’s my
                           password                                               2. “Here’s your
                           encrypted into                                           unique challenge
                           your challenge:                                    3          Luigi”
                                                        2
                           XYQWZY.”



                                      Access                       Carrier           Remote LAN
                                    Equipment                      Services          Access Server

                                                                                              LAN
      • Uses challenge-based encrypted password
      • Makes snooping much less effective
(Source: Ascend Corp)
                                          Token
                       2. User enters PIN
                          and challenge                    1. Challenge
                          into token                          received
                                                              from central site
       password          3. Token device
                            generates one-    Challenge:
                            time password      XYZ123

                         4. user enters         Enter
                                              password:      5. Password sent
                            password                            to central site
   Token Device             at prompt



          • Several types of token systems
          •Token generates exclusive one-time password
          •Requires possession of token device and PIN
Source: Ascend Corp.
Public Key Cryptography
 (A brilliant idea proposed in 1976)
Generating Keys

            Public Key




            Private Key
   Example Public Key:
-----BEGIN PGP PUBLIC KEY BLOCK-----
Version: PGPfreeware 7.0.3 for non-commercial use
<http://www.pgp.com>
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=w3hs
-----END PGP PUBLIC KEY BLOCK-----
Imagine a chest with two locks
                      Public Private
                     Keyhole Keyhole




  …now Imagine that you have the ability to generate such
  chests at will, and that they all react the same way to the
  keys belonging to it…as long as you have ONE key
  (either public or private, you can generate the chest…)
So, you want to send a secret
text to your friend, Billy-Bob?




                         Download Billy-
                         Bob’s Public Key
                                                           Billy-Bob
                                                           opens chest
                                                           using his
                                                           secret key
  You                                                     Billy-Bob
          Generate                          Send chest
          chest using                       with secret
          B-B’s Public                      text to
          Key + insert                      Billy-Bob
          secret text!
      Public Key Cryptography

•Sender encrypts message M into E(M) by applying
public key or encryption key (E) of receiver
•Receiver decrypts E(M) by applying her private key or
decryption key (D):
    i.e, D(E(M)) = M
Based on one-way (or trap door) functions which are
easy to compute in one direction but not in the other.
   – E: Encryption or public key
   – D: Decryption or private key
    But how do you prove to your
friend, Billy-Bob that you are YOU?
          (you already have his public key)




                                                                            Billy-Bob
                                        Billy-Bob tries YOUR public key     downloads
Use your own        Insert your         in the lock of the chest – if the   YOUR
                    chest inside        chest opens, it can only be from    public key
Private Key to
                    “his” chest!        YOU!
generate an                                                                  Billy-Bob
empty chest                                                                  opens chest
                                                                             using his
                                                                             secret key
    You                                                                     Billy-Bob
                 Generate
                 another chest                           Send chest(s)
                 using B-B’s                             to Billy-Bob
                 public Key
                Electronic signatures
                  (Another brilliant idea!)

• How do you convince your bank that you are indeed the
  sender of a message?
• Say Alice (A) is sending message to Bank (B):
   – Alice applies her decryption key DA (M )
   – Alice applies bank’s encryption key EB ( DA ( M ))
   – Sends message to bank
   – Bank applies its decryption key first :
       DB ( EB ( DA ( M )))  DA ( M )
   – Bank applies Alice’s encryption key E A ( DA ( M )))  M
• Based on the idea that keys are commutative, ie.
          E A ( DA ( M )))  DA ( E A ( M ))
          PGP (Pretty Good Privacy)
        (a.k.a. Phil’s pretty good software)
                http://www.pgp.com
• Software written by Phil Zimmerman (of Boulder fame!)
• Implements public key cryptography
• Available in public domain (on most Unix systems)
Basic commands
pgp -h       (for help)
pgp -kg      (to create your key)
pgp -e text_file her_user_id (to encrypt with recipient’s
                                               public key)
pgp ciphertextfile (to decrypt ciphertextfile)
pgp -ka keyfile      ( to add contents of a key file to your key
                                                        ring)
       Aircraft
       Downing in
       China
       •    “The airplane is basically a
            really big flying tape
            recorder”
       •    “Virtually anything
            transmitted through the air
            would be within reach”
       •    “…dozens of sensitive
            antennae pick up signals from
            radar, radio, cell phones,
            perhaps even e-mail”

       Source: The Daily Camera, April
          4th, 2001



EP-3E Source: NYT, April 4th, 2001
                   FIREWALLS



                                                   INTERNE
                                                   T




A firewall is a mechanism used to protect a trusted network from an
untrusted network. It implements the site's security policy and
is the single point in your network through which all communications
between the trusted and untrusted network must pass.
             Packet Filtering Firewalls
  -- Incorporate packet filters in the router software
  -- Reject/accept packets based on rules

Filter   Action Internal        Port External    Port     Comment
Rule             Host                 Host

   1     block      *       *        HACKER         *    deny access to


   2     allow     Mail         25     *            *    connect to mail
                                                         gateway

-- Generally anything not expressly permitted is prohibited.
      Application-Level Gateways
          (or Proxy Servers)
-- Use software applications to filter traffic for various services.

-- Program acts like a gateway (or proxy server), and

-- Logs traffic and forwards only the legitimate traffic.

-- Do not need rules as with packet level filters, but

-- Need a specialized program for each service (e.g. mail proxy,
       http proxy, etc.).
-- Operates at higher layer of OSI protocol.

-- Weakness:Runs on top of OS and subject to holes in OS.
    Internet Security Protocols
S-MIME: Secure Multipurpose Internet Mail Extensions.

SSL: Secure Socket Layer. SSL is a protocol for
transmitting encrypted data over TCP/IP networks.

S-HTTP: Secure HTTP. Security extension to HTTP to
protect individual transaction requests and responses.

SET: Secure Electronic Transaction. Developed by Visa
and MasterCard to support bank card payments involving
multiple parties (card holder, merchant, acquirer, issuer).
                Secure Web Transactions
Symmetric algorithms are faster than public key algorithms, but
public key algorithms are required to maintain privacy during the
exchange of the faster symmetric keys. To preserve both efficiency
and privacy, secure Web transactions begin with a public key
exchange, followed by the exchange of a session key that follows
a faster, symmetric algorithm.
                  Digital Certificate
    Is the cyberspace equivalent of a driver’s license.
    Way of authenticating yourself to other party.
SSL authentication is done by X.509 certificates.
Certificates are issued by certification authorities (CAs), e.g.
Verisign, GTE Cybertrust,etc., which act as trusted third parties.
Each certificate contains:
• information about the certificate's format.
• a unique serial number.
• information about the algorithm used to sign the certificate.
• the name of the CA which issued the certificate.
• the validity period of the certificate.
• identifying information about the "subject," or the entity to whom the
  certificate belongs,the subject's public key, and the issuer’s signature.
How SECURE ELECTRONIC
TRANSACTIONS (SET) WORK


                                 3. Bank Card Issuer
                      9. Customer gets 4. checks card          Card Issuer
                         monthly bill     authorizes
                                          transaction




                                           decrypts
                                  2. Merchant asks to
                                  8.
                                  7.           gets
                                  5. Bank authorizes
                                     “capture” transaction
                                     authorization
                                     transaction and
                                     paid                    Acquiring Bank
Customer    1. Customer gets goods + receipt
            6. Customer Initiates checks signature
                                     and get money
                 transaction with Order-form
                 + Signed + Encrypted
                 authorization




                                                               Merchant
      Problems with Encryption
• The Battle of Leyte Gulf (October 23-26 1944)
   – American navy forces split into two, each steaming to meet
     separate Japanese forces (located far away from each other)
       • Task Force 38 and Task Force 34 (commanded by Admiral Halsey)
   – Admiral Nimitz (in Pearl Harbor) was wondering about Task Force
     34’s position, sent message: “Where is Task Force 34?”
   – Cryptographer stuffed message, and sent it as:
       • “Turkey trots to water XX Where repeat where is Task Force 34 XX
         The world wonders.”
   – Halsey’s cryptographer, forgetting to remove all the stuffing, sent
     the following message to the bridge:
       • “Where repeat where is Task Force 34 XX The world wonders.”
Tennyson’s The Charge of the
       Light Brigade
      Half a league, half a league,
         Half a league onward,
       All in the valley of Death
         Rode the six hundred.
     "Forward, the Light Brigade!
    "Charge for the guns!" he said:
       Into the valley of Death
         Rode the six hundred.
Tennyson’s The Charge of the
       Light Brigade
   Flash'd all their sabres bare,
   Flash'd as they turn'd in air,
    Sabring the gunners there,
    Charging an army, while
     All the world wonder'd:
                 …
   Then they rode back, but not
       Not the six hundred.
                       Key Security Points

     High-level security consists of multiple system components:
      User identification
      Access verification
      Security administration
     Combine multiple security mechanisms for desired level of
      security
     Both dial-up security and backbone security are important.
     Individual responsibility is essential!



Source: Ascend Corp.
                         Security Resources
       • CERT: Computer Emergency      http://www.cert.org/
         Response Team                    1-412-268-7090

       • CSI: Computer Security        http//www.gocsi.com
         Institute                        1-415-905-2626

       • ISSA: Information Systems     http://www.issa-intl.org/
         Security Association             1-708-699-6441

       • TruSecure Corporation         http://www.trusecure.com
         (formerly National Computer      1-717-258-1816
         Security Association)

       • FIRST Forum of Incident       http//www.first.org
         Response and Security Teams
Source: Ascend Corp.